1. Field of the Invention
The present invention relates to a fuel cell comprising a fuel cell unit composed of an electrolyte interposed between an anode electrode and a cathode electrode, separators for supporting the fuel cell unit interposed therebetween, and a fluid passage for allowing a fluid such as a cooling medium to flow in a superficial direction of the separator.
2. Description of the Related Art
For example, the solid polymer electrolyte fuel cell comprises a fuel cell unit including an anode electrode and a cathode electrode disposed opposingly on both sides of an electrolyte composed of a polymer ion exchange membrane (cation exchange membrane), the fuel cell unit being interposed between separators. Usually, the fuel cell is used as a fuel cell stack comprising a predetermined number of fuel cell units and a predetermined number of separators which are stacked with each other.
In such a fuel cell, a fuel gas such as a gas principally containing hydrogen (hereinafter referred to as xe2x80x9chydrogen-containing gasxe2x80x9d), which is supplied to the anode electrode, is converted into hydrogen ion on the catalyst electrode, and the ion is moved toward the cathode electrode via the electrolyte which is appropriately humidified. The electron, which is generated during this process, is extracted for an external circuit, and the electron is utilized as DC electric energy. An oxygen-containing gas such as a gas principally containing oxygen (hereinafter referred to as xe2x80x9coxygen-containing gasxe2x80x9d) or air is supplied to the cathode electrode. Therefore, the hydrogen ion, the electron, and the oxygen gas are reacted with each other on the cathode electrode, and thus water is produced.
In order to supply the fuel gas and the oxygen-containing gas to the anode electrode and the cathode electrode respectively, a porous layer having conductivity, for example, porous carbon paper is usually disposed on the catalyst electrode layer (electrode surface), and the porous layer is supported by the separator. Further, one or a plurality of gas flow passages designed to have a uniform widthwise dimension are provided on the mutually opposing surfaces of each of the separators. On the other hand, a cooling medium passage is formed on the surface of the separator disposed on a side opposite to the surface provided with the gas flow passage, with which it is intended that the heat generated by the power generation of the fuel cell unit is effectively removed.
Such a technique is represented, for example, by a solid polymer electrolyte fuel cell disclosed in Japanese Laid-Open Patent Publication No. 10-50327, in which a separator plate 1 is provided with a cooling medium passage 2 as shown in FIG. 12. The cooling medium passage 2 is constructed to make communication with a cooling water inlet 3 and a cooling water outlet 4 so that the cooling water is allowed to flow in the direction of the gravity while meandering in the horizontal direction.
However, in the case of the conventional technique described above, the flow passage length of the cooling water passage 2 is considerably long, and many bent portions inevitably exist, because the cooling water is allowed to flow in the direction of the gravity with the cooling medium passage 2 meandering on the surface of the separator plate 1. For this reason, the following problem is pointed out. That is, the flow passage pressure loss is large, and the system efficiency of the power generation of the entire fuel cell is lowered.
A principal object of the present invention is to provide a fuel cell which makes it possible to effectively avoid the pressure loss in a fluid passage provided in a superficial direction of a separator, and improve the system efficiency of the power generation.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.